No deal has been finalized, but the Miramar-based budget carrier has been in talks with Miami International Airport and Miami-Dade county officials for months about the possibility.

“They want to move a number, if not a bulk, of their operations to MIA,” Miami-Dade County Mayor Carlos A. Gimenez told the Miami Herald last week.

While Spirit won't comment on specific plans for growth, a spokeswoman said there are no plans to abandon Fort Lauderdale-Hollywood International Airport, where the airline is the No. 3 carrier.

“We have no plans to move the FLL base,” Spirit spokeswoman Maggie Espin-Christina said in an email. “FLL is a very important, successful and profitable piece of our network. We talk to airports all the time and, while Miami does qualify as one of the many airports that could benefit from our low fares, there is nothing to announce at this time.”

Spirit has 45 flights a day at the Fort Lauderdale airport, where it has lease obligations through late 2016. In 2013, the airline had more than 18 percent of the market share at FLL, carrying nearly 4.3 million passengers to and from the airport.

Through February of this year, the airline flew 743,505 passengers, a more than 7 percent increase over the same period in 2013.

“Spirit is a good partner and has a good working relationship with Broward County,” said Gregory Meyer, spokesman for the Broward County Aviation Department. “Our airport and their airline have grown together. We have no information indicating that Spirit plans to relocate their operations from Fort Lauderdale-Hollywood International Airport to any other airport in the region.”

Spirit flies to more than 50 destinations in the U.S., Latin America and Caribbean, with more than 250 flights a day. Last year, the airline started service to 25 new markets. In its annual report filed in February, the publicly traded company said it has already established “a substantial network of destinations in profitable U.S. domestic niche markets.”

The airline, well known for its quirky ads and add-on fees for everything from carry-on luggage to bottled water, said it has also grown into large markets where higher airfares have made flying difficult for price-sensitive travelers.

“Our strategy to balance growth in large domestic markets, niche markets and opportunities in the Caribbean and Latin America gives us a significant number of growth opportunities,” the report says.

Spirit has never flown out of Miami International Airport, which has only a handful of international low-cost carriers. MIA is more expensive for airlines than Fort Lauderdale, where the top three carriers are low-cost companies with nearly 57 percent of the market combined.

Separate statements from Gimenez and the airport on Tuesday indicated that talks with Spirit about starting operations at MIA have been ongoing for “many months” with nothing yet final.

“That said, I would gladly welcome Spirit Airlines should they include MIA in their future growth plans,” Gimenez said.